Reamers for enlarging bore holes drilled for oil wells and mine shafts have been known in the drilling art for many decades. Typically, a reamer includes a central body having three or more roller reamer units mounted at circumferentially spaced intervals around the tool body. The reamer tool is mounted in a string of drill pipe (drill collars) or other rotatable pipe such that the reamer is rotated with the drill pipe through the well bore in order to enlarge the bore. The roller reamer units rollably engage the well bore wall to enlarge the bore as the drill string moves through the hole. Roller reamers are used to roll against the hole wall of an in-gauge hole to reduce the torque of the drill collars against the hole wall of a directionally drilled hole. An example of a roller reamer tool is found in U.S. Pat. No. 3,977,481 of Fisk which discloses three roller reamer units mounted on a tool body. Each roller unit includes a centrally mounted shaft having the roller mounted onto the shaft for rotation therewith. The shaft and roller mount upper and lower thrust bearings and seal rings to seal off an internal region between the shaft and the roller. This internal region is lubricated utilizing a pressure balancing internal piston to maintain lubrication in spite of variations in pressure surrounding the tool.
Another example of such a roller reamer is found in U.S. Pat. No. 4,182,425 of Garrett which discloses in several embodiments roller reamers having a variety of features. These roller reamers are mounted in position on cylindrical bearing blocks which fit in cylindrical recesses in the tool body. The roller reamers include rollers or cutters which are mounted onto a stationary shaft and are held against thrust by a series of ballbearings or, in a different embodiment, by a thrust flange. Additionally, a lubricant is sealed in between the stationary shaft and the rollers. The lubricant may be held in the region between the stationary shaft and the rotating roller or cutter by means of a flexible diaphragm which acts to equalize the pressure within the lubricating region. In order to remove the cylindrical blocks shown in U.S. Pat. No. 4,182,425 it is necessary to place some type of tool in a recess behind the blocks to push them radially outwardly.
U.S. Pat. No. 4,428,626 of Blau discloses a roller reamer tool wherein two roller units are placed along the same axis and held in position by a combination of end bearing blocks and a central retainer pad which includes a jack screw for removal of the pad from its detented position in the body. These are only examples of a large variety of constructions of roller reamers in the prior art.